Method of preventing rearrangement of blocked copolyesters



Dec. 9, 1969 SMITH ETAL 3,483,157

METHOD OF PREVENTING REARRANGEMENT OF BLOCKED COPOLYES'IERS OriginalFiled July 2, 1962 5 sheets*sheet l PRECIPITANT RECORDER E II [i 5 7LIGHT SOURCE INCIDENT O"; PHOTO BEAM CELL PRECIPITATION CURVE OF TYPICALFIBER-FORMING COPOLYESTER PRECIPITATED FROM 60-40PHENOL-TETRACHLORETHANE WITH METHANOL 90 g 80 5 7O 2 so 5 so 40 0C ml OFPREClPlTANT FIG.2

JAMES G. SM|TH CHARLES J. KIBLER ROGER M. SCHULKEN,JR.

INVENTORS I BYk/WJM M/L H ATTORNEYS Dec. 9, 1 J. 6. SMITH ETAL 3,483,157

METHOD OF PREVENTING REARRANGEMENT OF BLOCKED COPOLYESTERS iginal FiledJuly 2, 1962 5 Sheets-Sheet 3 ATTORNEYS Burg/m4 NOISSIWSNVELL 5Sheets-Sheet 4 D 9, W69 J. cs. SMITH ETAL METHOD OF PREVENTINGREARRANGEMENT' OF BLOCKED COPOLYESTERS Original Filed July 2, 1962 22018JOz IhmEEmZ xmIOJo 0 20mm mmmkmmhamoo ATTORN YS NOISSIWSNVHJ. BY

United States Patent M 3,483,157 METHOD OF PREVENTING REARRANGEMENT OFBLOCKED COPOLYESTERS James G. Smith, Charles J. Kibler, and Roger M.Schulken, Jr., Kingsport, Tenn., assignors to Eastman Kodak Company,Rochester, N.Y., a corporation of New Jersey Original application July2, 1962, Ser. No. 206,755. Divided and this application Oct. 16, 1967,Ser. No. 720,003

Int. Cl. 008g 51/56, 17/08 U.S. Cl. 26031.2 6 Claims ABSTRACT OF THEDISCLOSURE The rearrangement or randomization of a blocked copolyestermay be prevented by treating said blocked copolyester with an arseniccompound.

This application is a division of Smith, Kibler, and Schulken U.S. Ser.No. 206,755, filed July 2, 1962, abandoned in favor of continuingapplication Ser. No. 678,457, in turn abandoned in favor of continuingapplication 776,311, now Defensive Publication dated May 27, 1969.

This invention relates to copolyesters derived by the condensation ofcisand trans-cyclohexanedimethanol and one or more dicarboxylic aromaticacids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc, modified with one or more of the aliphaticdicarboxylic acids such as succinic, glutaric, adipic, pimelic, sebacic,suberic and the like. More specifically the invention relates to the socalled blocked copolyesters of this type in which repeat units of themajor components, such as the unit derived from the condensation ofterephthalic acid and 1,4-cyclohexanedimethanol, and the repeat units ofthe minor component, such as the unit derived from the condensation ofsebacic acid and 1,4-cyclohexanedimethanol, are not randomly distributedalong the polymer chain but occur in large discrete groupings termedblocks. Even more specifically the invention relates to a means andmethod of preventing the rearrangement or randomization of these repeatunits under conditions in which blocked copolyesters are held in themolten state for appreciable periods of time, as in the case in theemployment of these compositions in the production of fibers andfilaments by the melt spinning process or by the formation of films,sheets and other shaped objects by extruding a molten mass of thecopolyester material through a shaping orifice.

For purposes of a clearer understanding of the present invention and thephenomena upon which it depends, a discussion of the essential elementsof the problems in the extrusion of blocked copolyester compositions isdesirable at this point. As is now known from numerous patent and otherdisclosures in the technical literature, high melting high molecularweight, linear copolyesters of the fiber and film forming variety havecome into prominence in recent years. For example U.S. Patent No.2,901,466 to Kibler, Bell and Smith, issued Aug. 25, 1959, disclosuressuch copolyesters which have outstanding value in the production offibers, filaments, films and other shaped objects. These copolyestersare typical of the compositions dealt with in the present invention.

While the phenomenon of blocking in the production of copolyesters hasbeen recognized by other workers in the field of polymer chemistry, asfor example D. H. Coffey and T. J. Meyrich in Proceedings of the RubberTechnological Conference, London (1954), pages 170'- 184, published in1956, so far as we are aware none of these researchers have recognizedthe desirability of maintaining the original arrangement of the polymer3,483,157 Patented Dec. 9, 1969 blocks in a copolymer, and of coursehave not suggested any means of preventing rearrangement orrandomization. To the best of our knowledge and belief the presentinvention involves the first recognition of this problem and a means forits solution.

Before discussing the specific invention which is the subject of theinstant invention it is desirable to discuss two terms which will beemployed frequently hereinafter, that is, random copolyester and blockcopolyester. The concept of random and block polymers has existed for anumber of years. Indeed, in the field of vinyl polymers, these termsfind frequent usage. It is much less common to find references to blockpolymers in the field of condensation polymers, such as polyesters orpolyamides. A copolyester is, of course, one which is prepared from atleast three dilTerent reagents, two of which form the basic polyesterand the third (or others) constitutes the modifying agent. The first twoare customarily a diol and a dicarboxylic acid or a reactive derivativethereof. The modifying agent can be a diacid (or reactive derivative), adiol, a hydroxy acid, etc.

In a random copolyester, the molecular units derived from the modifyingagent or agents are distributed at random in the linear chain ofmolecular units derived from the principal diacid and diol.Specifically, a polyester prepared from three molecular parts ofterephthalic acid, one molecular part of sebacic acid and four molecularparts of 1,4-cyclohexanedimethanol contains two different molecularunits, one which can be designated (A) derived from terephthalic acidand 1,4-cyclohexanediamethanol and the other, designated (B), derivedfrom sebacic acid and 1,4-cyclohexanedimethanol, thus:

Since there are three A'groups for every B group in the final polyester,the struture of the random copolyester can be represented by a randomlinear combination of As and Bs in the ratio of three to one, as forexample,

However, the structure of the block copolyester can be represented by alinear combination of As and Bs in which the two groups are collected inclusters or blocks,

such as:

wherein T designates the melting point of the unmodified base polymer, Kdesignates a constant and In designates the natural logarithm. In thecase of a block co' polymer, the melting point approaches that of thepolyester repeat unit which is present as the major component, since themodifying units, B, are grouped in clusters and each of these clustersbehaves as a single molecular unit insofar as its effect on the meltingpoint of the blocked copolyester is concerned.

The blocked copolyesters of the instant invention are prepared from (A)at least one glycol and (B) at least one dibasic acid comprising atleast 60 mole percent of an acid having two carboxyl radicals attachedto a carbocyclic nucleus having from 6-20 carbons per ring, in whichcopolyester at least three components are present, one of which can bepresent as an isomer of one of the other two components, saidcopolyester, if of the fiberand film-forming type, having a number ofaverage molecular weight between 8,000 to about 100,000, an inherentviscosity in a mixture of 60 percent phenol and 40 percenttetrachloroethane of at least 0.6, such viscosity being calculated fromthe equation:

wherein 1 is the ratio of the viscosity of a dilute (approximately .25percent by weight) solution of the polymer in a solvent composed of 60percent by weight of phenol and 40 percent by weight oftetracholorethane to the viscosity of the solvent itself, and C is theconcentration of the polymer in grams per 100 cubic centimeters of thesolution, said copolyester having a melting point differential of from10 C. to 50 C. above the melting point of the corresponding randomcopolyester.

Block copolyesters of the type referred in the preceding paragraph maybe prepared by either one of two methods. The first method is thesubject of an application in the name of Charles J. Kibler, Nicholas C.Russin and Alan Bell, Ser. No. 801,705, filed Mar. 25, 1959, entitledLinear Abnormalized Block-Type Copolyesters. now US. Patent 3,117,950.Essentially this process involves first preparing a low molecular weightcopolyester and heating this copolyester at a temperature below itsmelting point so that a conversion of the random copolyester structureto a blocked copolyester occurs. The low molecular weight blockedcopolyester is then further polymerized in the solid phase by well knowntechniques, such as by heating the polymer under vacuum at elevatedtemperatures until the desired viscosity is reached.

The second method is the subject of an application in the name of JamesG. Smith and Charles J Kibler, Ser. No. 185,992, filed Apr. 9, 1962, andnow abandoned, entitled Block copolyesters, and involves first preparingeither a high molecular weight polymer or a low molecular weightcopolyester and heating this material in the molten state at atemperature selected from a range whose lower limit is defined by themelting point of the random copolyester prepared and whose upper limitis defined by the melting point of the completely blocked copolyester ofthe same composition.

As will be apparent to those skilled in the art to which this inventionrelates, it is highly desirable that the fiberand film-formingcopolyesters here dealt with shall maintain their desirable physicalproperties such as ready dyeability, high impact strength, satisfactoryelongation, high melting point, high fiber sticking temperature and highfabric stiffening temperature when such copolyesters are converted intofibers, filaments, films, sheeting, and other shaped objects by thevarious melt extrusion processes employed for this purpose. The idealsituation with respect to the melt-spinning of fibers and films fromsuch compositions would be to have no change occur in the copolyesterstructure or arrangement of the molecular blocks but experience hasshown that when such composi tions are subjected for any appreciablelength of time to the effect of temperatures required to bring them intoa molten condition and cause them to be sufficiently fluid to beextrudable a change takes place which involves a rearrangement orrandomization of the molecular blocks. In other words, when blockedcopolyesters are melt spun or molded a randomization of distribution ofthe molecular blocks occurs if the polymer is held in the molten statefor more than a few minutes. It has been found that the polymericmaterial of the fibers or molded objects produced under suchcircumstances consist essentially of the randomized copolyester unlessvery high speed extruding is employed and that such products suffer anadverse change in those physical properties related to the high meltingpoint of the blocked copolyesters. For example, the fiber stickingtemperature and the fabric stiffening tempterature of the textile goodsobtained by the normal melt spinning process are found to be much lowerthan is the case with those textile materials obtained by usingcopolyesters which have completely retained their blocked molecularpattern or structure. Thus is will be evident that the maintenance ofthe original molecularly blocked arrangement of the copolyester materialduring melt spinning or other melt extrusion operation is highlyimportant and in fact critical to the successful employment of thisdesirable type of material for such purposes.

It is accordingly the principal object of the instant invention toprovide a means and method whereby the original arrangement of themolecular blocks of a blocked copolyester may be maintained forsubstantial periods of time.

Another object is to provide a means and method whereby the originalarrangement of the molecular blocks of a blocked copolyester may bemaintained for a substantial length of time in the molten state.

A further object is to provide a means of preventing the randomizationof the molecular units or blocks of a blocked copolyester of the fiberand film-forming type.

Another object is to provide a blocked copolyester stabilized againstrandomization or rearrangement of its molecular units or blocks andadapted for the melt spinning of fibers, filaments, films and othershaped objects.

A further object is to provide improved copolyester fibers, films, andother shaped objects having a useful and advantageous combination ofphysical properties, namely good elongation, high melting point, lowsolubility, high heat distortion temperature, high fiber stickingtemperatures, high fabric stiffening temperature, ready dyeability andthe like.

Other objects will appear hereinafter.

These objects are accomplished by the following invention which is basedupon the discovery that the catalyst which is employed to catalyze theoriginal condensation reactions involved in production of thecopolyester itse'f remains in the polymer substance (because no knownpractical means is available for its removal) is also an effective agentfor rapid conversion of the molecular blocked copolyester to the randomstructure when the blocked copolyester is held in the molten state forappreciable periods of time. We have also found that when this catalystis converted into an inactive form its effect thus to produce therandomization structure of the blocked copolyester is very markedlyreduced or eliminated.

For example, in the production of copolyesters in accordance with theabove description, as by the process described in the Kibler, Bell andSmith US. Patent 2,901,466, the catalyst employed may be a titaniumcompound and preferably one of the titanium magnesium complexesfrequently referred to as a Meerwein complex" as described in John R.Caldwells U.S. Patent 5 2,720,502 issued Oct. 11, 1955. These catalystshave the general formula structures set forth below:

wherein M is an alkali metal, e.g. lithium, sodium, or potassium, M' isan alkaline earth metal such as Mg, Ca or Sr, and R is an alkyl radicalcontaining from 1 to 6 carbon atoms; R can be derived from a loweraliphatic alcohol such as methyl, ethyl, propyl, n-butyl, isobutyl,n-amyl etc. Specific examples of such catalyst are N 4 9)6) 2 s)s)z,

and KH(Ti(OCH Other catalysts which may be employed for this purpose aredescribed in US. Patent to Haslam No. 2,822,348 issued Feb. 4, 1959 as,for example, titanium tetraisopropoxide.

In accordance with the invention we have found that, so far asrandomization of the blocked copolyester is concerned, the adversecatalytic effect of the condensation catalyst above referred to can besubstantially reduced or eliminated by one of two methods. The firstmethod invoIves the treatment of the blocked copolyester in powderedform with stream at a high temperature selected from the range of 100 to200 C. for periods ranging from one quarter to twenty hours, dependingupon the composition and whether atmospheric or superatmosphericpressures are employed. Under these conditions we have found that thesteam converts the catalyst present in the polyester to an inactive formwhich is believed to be a hydrated titanium oxide. In such form thecatalyst is no longer effective in converting the blocked structure ofthe copolyester to a form in which the random arrangement of themolecular or repeat units occurs. Thus there is provided a verypractical and ultilitarian method of so controlling the arrangement ofthese molecular and repeat units as to enable the treated copolyestersproduced in accordance with the invention to be converted into shapedarticles by the usual melt spinning or melt extrusion processes withoutthe use of special extrusion techniques or special equipment. Thus thefinal shaped articles can be formed from polymeric material which has anessentially completely blocked molecular pattern or structure, whereaswithout the steam treatment described hereinabove the molecularlyblocked copolyester would rearrange to the random structure under thetemperatures normally employed in melt extrusion processes.

The other method of obtaining the aforesaid advantages involvesneutralizing the adverse catalytic influence of the catalyst on therandomization of the blocked copolyester material by treating theblocked copolyester with 0.005-0.5 percent by weight of copolyester ofan arsenic compound such as arsenic pentoxide, whereby the condensationcatalyst present in the copolyester is a so conerted to an inactiveform, probably a molecular complex of titanium and arsenic of unknownchemical structure.

DETERMINATION OF THE EXTENT OF BLOCK- ING OF A POLYESTER Thedetermination of the extent of b ocking of a polyester, in this case acopolyester, is based on the measurement of melting point or solubilityin any solvent which will dissolve the maferial to an appreciabe extent.In a randomized copolyester as above described the melting pointdecreases and the solubility increases in proportion to the amount ofthe modifying component. For example in the case of the copolyesterprepared by a condenzation reaction between dimethyl terephthalate,dimethyl sebacate and 1,4-cyclohexanedimethanol the melting point of thefinal random copolyester decreases as the amount of the modifying agent,in this case dimethyl sebacate, is increased and the solubility of thefinal random copolyester increases as the amount of the modifying agent,dimethyl sebacate, increases. In a completely blocked copolyester havingthe configuration of molecular units as described above, the meltingpoint and solubility of the final blocked copolyester approximate themelting point and solubility of the major unmodified polyestercomponent, in this case, the 1,4-cyclohexanedimethanol terephthalatecomponent.

While the melting point of such copolyesters can be determined by simpleand conventional methods, the determination of solubility of the polymerrequires a special technique. Specifically, solubility may be determinedthrough determination of the precipitation curve of .the polymer and themethod will be described in detail below. In all of the references tosolution of the copolyester it is to be understood that the material isdissolved in a solvent composed of 60 parts by weight of phenol and 40parts by weight of tetrachloroethane and the precipitating solventemployed is methanol.

In the accompanying drawing:

FIGURE 1 is a diagrammatic illustration of an apparatus determining theprecipitation curves of a copolyester of the type to which the instantinvention relates.

FIGURE 2 shows a typical precipitation curve obtained on a copo'yestercomposition of the subject invention which was obtained through the useof the apparatus shown schematically in FIGURE 1.

FIGURE 3 is a set of precipitation curves of (A)po'y(1,4-cyclohexylidenedimethylene terephthalate), a typical randomcopolyester of the fiber and film forming variety containing no secondmodifying acid, and of other random copolyesters of this type (B), (C),(D), which have been modified by varying amounts of a second modifyingacid.

FIGURE 4 is a set of precipitation curves of copolyesters derived fromthe condensation of terephthalic acid and 1,4-cyclohexanedimethanol andmodified with succinic acid in varying amounts (E), (F) beforemelt-spinning into fibers, and precipitation curves (G), (H) of thesesame copolyester compositions after they have been subjected tomelt-spinning into fibers.

FIGURE 5 is a set of precipitation curves similar to those of FIGURES 3and 4 and illustrating the effect on a blocked copolyester (Curve F ofFIGURE 4) by treatment with steam in accordance with the invention, (1)being the precipitation curve obtained on a sample of yarn which wasmelt-spun from the blocked copolyester of Curve F after the blockedcopolyester had been treated with steam under pressure for one hour atC., (I) being the precipitation curve on a sample of yarn meltspun froma copolymer obtained by the same treatment as applied to the copolyesterof Curve F but for only onehalf hour at the same temperature, (K) beingthe precipitation curve on a sample of yarn melt-spun from a copolymerobtained by treating the same copolyester of Curve F at the sametemperature for only an extremely short time of the order of two orthree minutes, (H) being the precipitation curve of the same copolyesterof Curve F after having been spun into yarn but untreated with steam and(L) being the precipitation curve of a sample of film which had beenheld in the molten state for four minutes at 280 C. and obtained usingthe polymer of Curve P which had been treated with steam under pressurefor one hour at 150 C.

FIGURE 6 is also a set of precipitation curves illustrating the effecton a blocked copolyester of steam treatment at atmospheric pressure inaccordance with the invention, (M) being the precipitation curve of theblocked copolyester which has been subjected to steam treatment forfifteen hours at atmospheric pressure, (N) being the precipitation curveobtained on a sample of the copolyester of Curve M which had beenpressed into a film and held in a molten state for four minutes, beingthe precipitation curve obtained on a sample of film which had beenpressed and held in the molten state for four minutes from a blockedcopolyester of the same composition as that of Curve M but which hadbeen treated with steam for only six hours and (P) being theprecipitation curve obtained on a sample of film which had been pressedand held in the melt for four minutes from a sample of the blockedcopolyester of the same composition as that of Curve M, the originalpolyester having received no steam treatment at all.

The apparatus and experimental procedure used in the determination ofthe precipitation curves above referred to resemble very closely thosedescribed by D. R. Morey and I. W. Tamblyn in J. Applied Physics, volume16, pages 419-424, 1945. The chief difference is in the solvent and theprecipitant used to accommodate the polyester.

The apparatus centers about a square glass cell 1 illuminated by aparallel beam of light from a light source 3 which may, for example, bea 100 watt Bausch and Lomb microscope lamp. The cell is thermostated at25 C. with a water bath 4 equipped with a stirrer 10 and appropriatewindows 5 and 6 for illumination of the cell. The directly transmittedlight beam 2 impinges on a photocell 7 the output of which is led to arecorder 8. A variable resistance 9 is provided in the circuit so thatthe output range of the photocell is accommodated by the range of therecorder.

The polymer to be studied is dissolved in 60:40 phenol:tetrachloroethane at a concentration of 0.05 percent. This solution isplaced in the cell, so that the incident beam is completely within thesolution. The solution is stirred by stirrer 10 and permitted to come toequilibrium with the temperature of the cell. The recorded output of thephotocell now corresponds to 100 percent transmission of the incidentbeam.

The precipitation curve determination is initiated by starting amechanical pump, not shown, which delivers one ml. of methanol perminute to the solution in the cell through supply conduit 11. The chartspeed of the recorder 8 is /2 inch per minute so that one inch of chartlength corresponds to 2 ml. of precipitant. As the precipitant is added,it is rapidly mixed into the solution by the stirrer. Usually, there isno change in transmission of the light during addition of the first fewml. of precipitant. However, eventually a point is reached where thepolymer begins to precipitate and produce a haze in solution whichreduces the amount of light which is directly transmitted through thesolution and as a result the percentage transmission recorded on therecorder begins to decrease. As more and more precipitant is metered in,more and more polymer precipitates and the percentage transmissionprogressively decreases. Finally all the polymer has precipitated andthe percentage transmission reaches a constant low value. The curvetraced out by the recorder resembles that shown in FIGURE 2. It can beseen, then, that such a curve is a valuable indication of the relativesolubilities of polymers. An insoluble polymer will require very littleprecipitant to initiate the precipitation; a soluble polymer willrequire a much greater volume of precipitant to initiate theprecipitation.

In the following examples and description we have set forth several ofthe preferred embodiments of our invention but they are included merelyfor purposes of illustration and not as a limitation thereof.

The method of preventing randomization of blocked co polyesters inaccordance with our invention will be conveniently illustrated by thefollowing examples of typical procedures carried out in accordancetherewith.

In order more clearly to illustrate our invention reference is made tothe curves of FIGURE 3 which are precipitation curves of randomcopolyesters as identified above, which copolyesters are precipitatedfrom solutions in 60:40 phenolztetrachloroethane by methanol andillustrating the increasing amount of precipitant required to obtainprecipitation of these copolyesters with increasing amounts of themodifying second acid in the copolymer. In all the cases it will beunderstood that the determination of these precipitation curves is bythe method and apparatus to which reference has been made above and asillustrated in FIGURES 1 and 2. Referring now to Curve A of FIGURE 3this curve was determined from the precipitation of the unmodified basepolymer, poly(1,4-cyclohexylidenedimethylene terephthalate) from a .05percent solution of the polymer in 60:40 phenol tetrachloroethane bymethanol.

Curve B of FIGURE 3 was determined by precipitating the copolyesterprepared from 1,4-cyclohexanedimethanol, 3 molar equivalents ofterephthalic acid and one molar equivalent of succinic acid.

Curve C of FIGURE 3 was determined by precipitating a copolyesterprepared from l,4-cyclohexanedimethanol, 3 molar equivalents ofterephthalic acid and 1 molar equivalent of sebacic acid.

Curve D of FIGURE 3 was determined by precipitating a copolyesterprepared from 1,4-cyclohexanedimethanol, 3 molar equivalents ofterephthalic acid and 2 molar equivalents of succinic acid.

This set of curves clearly demonstrates that in the case of a randomcopolyester the solubility of the copolyester increases as the amount ofthe second modifying acid in the copolymer is increased. For example thecopolymer used in determining Curve D of FIGURE 3 requires approximately4 times the volume of precipitant to precipitate the polymer than doesthe unmodified base polymer used in obtaining Curve A of FIGURE 3.Hence, the polyester composition of Curve D is much more soluble thanthat of Curve A. Similarly the copolyester compositions used inobtaining Curves B and C of FIGURE 3, which have an intermediate amountof modifying acid, have also an intermediate solubility.

Reference is now made to the curves of FIGURE 4. These are precipitationcurves of blocked copolyesters and of yarns derived therefrom fromsolutions of 60:40 phenolztetrachloroethane. Referring now to Curve E ofFIG- URE 4, this curve was obtained by precipitating a blockedcopolyester prepared from 1,4-cyclohexanedimethanol, 3 molar equivalentsof terephthalic acid and one molar equivalent of succinic acid andconverted to the molecularly blocked structure by the process of Kibleret al., Ser. No. 801,705, filed Mar. 25, 1959, now US. Patent 3,117,950entitled Linear Abnormalized Block-Type Copolyesters above referred to.Curve F of FIGURE 4 was obtained by the precipitation of the copolyesterprepared from 1,4-cyclohexanedimethanol, 3 molar equivalents ofterephthalic'acid and 2 molar equivalents of succinic acid and alsoconverted to the molecular blocked structure by the process of Kibler etal. mentioned above.

Curve G of FIGURE 4 is the precipitation curve of the yarn obtained bymelt-spinning the molecularly blocked copolyester represented by Curve Eof FIGURE 4.

Curve H of FIGURE 4 is the precipitation curve of the yarn obtained bymelt-spinning the molecularly blocked copolyester represented by Curve Fof FIGURE 4.

The diiferences between the random copolyesters and the block-typecopolyesters, particularly in their behavior, will now be elucidated bya comparison of certain of the curves of FIGURE 3 with those of FIGURE4. Comparing Curve B of FIGURE 3 and Curve E of FIGURE 4, it can be seenthat these two polyesters which have an identical chemical compositionshow a marked difference in their precipitation curves, the polyesterrepresented by Curve E of FIGURE 4 being much less soluble than thatrepresented by Curve B of FIGURE 3 as is clearly indicated by thesmaller volume of methanol required to effect precipitation of thepolyester of Curve E than was required in the case of the polyester ofCurve B. This difference in solubility is due to the difference inmolecular arrangement of the chemical repeat units of the twopolyesters. In the' case of the polyester of Curve B of FIG- URE 3, thechemical repeat units are randomly arranged along the length of thepolymer molecule. In the case of the polyester of Curve E of FIGURE 4,the chemical repeat units are arranged together in such a manner thatthe majority of the repeat units due to the modifying acid are groupedin a relatively few clusters or blocks. Each of these blocks behaves asa single modifying entity and as such has a relatively minor efiFectupon the solubility of the copolyester. The solubility characteristicsof a copolyester which has been molecularly blocked in this manner tendto resemble those of the completely unmodified polyester present as themajor constituent. In this case this major constituent ispoly(1,4-cyclohexylidenedimethylene terephthalate). Attention isspecifically directed to the close resemblance of the precipitationCurve E of FIG- URE 4 and that of Curve A of FIGURE 3, the latter curvebeing the precipitation curve obtained on the unmodified base polymerpoly(1,4-cyclohexylidenedimethylene terephthalate) When the polymerrepresented by Curve E of FIGURE 4 is melt spun into a fiber, theblocked structure originally present in the polymer is found to bepartially or completely absent in the yarn so obtained. This can beillustrated by an examination of Curve G of FIGURE 4 which, as mentionedabove, is the precipitation curve obtained on the yarn melt spun fromthe copolyester composition represented by Curve E of FIGURE 4. It canbe seen that the yarn requires much more precipitant to produce theprecipitation Curve G than did the original polymer. It can also be seenthat the Curve G of FIGURE 4 resembles very closely that of Curve B ofFIGURE 3. Curve B of FIGURE 3 represents the precipitation curveobtained on an essentially random copolyester composition identical tothat of Curve E. Hence it must be concluded that the molecularly blockedstructure present in the copolyester represented by Curve E of FIGURE 4is no longer present, or present to a greatly reduced extent, in themelt spun yarn obtained therefrom.

A similar situation can be demonstrated to occur with a polyester of adifferent composition. Comparing Curve D of FIGURE 3 with Curve F ofFIGURE 4 it can be seen that these two polyesters, which again have anidentical chemical composition, show a marked difference in theirprecipitation curves. Again it is concluded that the polyestercomposition represented by Curve F of FIG- URE 4 has a molecularlyblocked chemical structure and consequently requires a much smallervolume of precipitant to generate the precipitation Curve F than doesthe polyester composition which has a random molecular structure asrepresented by Curve D.

Again, when the blocked copolyester represented by Curve F of FIGURE 4is melt spun into a yarn the blocked molecular structure is converted toa random structure. This can be demonstrated by considering Curve H ofFIG- URE 4 which is the precipitation curve of the yarn melt spun fromthe polyester composition represented by Curve F of FIGURE 4. It can beseen that the yarn requires much more precipitant to generate theprecipitation curve than does the original polymer.

Still again, the precipitation Curve H of FIGURE 4 closely resembles theprecipitation Curve D of FIGURE 3 which is the curve obtained from arandom copolyester of the same chemical composition.

It must be concluded then that under the melt spinning conditionsnormally employed, a molecularly blocked copolyester is generallyconverted wholly or in part to a random molecular structure unless theprocesses of the instant invention are employed to slow or stop thismolecular rearrangement of the chemical repeat units.

The above discussion of the precipitation curves of FIGURES 3 and 4 isintended to serve primarily as an elucidation of the problem dealt withby the instant invention. The solutions of the problem providedaccording to the invention will now be discussed by reference to certainspecific examples and other description.

As previously indicated, in accordance with one embodiment of ourinvention the copolyester in powdered or other comminuted form istreated with high temperature steam for a certain period of time duringwhich the activity of the catalyst present in the material to causerandomization of the blocked structure of the copolyester is reduced oreliminated by conversion of the catalyst into an inactive form in whichit has reduced tendency, or no tendency, to catalyze randomization. Forexample employing steam at atmospheric pressure and at C. the powderedcopolyester may be steam treated for a period ranging from 1-20 hours.On the other hand, when employing steam at superatrnospheric pressurethe temperature may range from 100 to 200 C. for a period ranging fromtwo minutes to two hours. In this connection it should be noted that anytreatment of the block copolyester with steam, even for short periods,occasions a degree of stabilization of the copolyester againstrandomization of the molecular or repeat units thereof. By the sametoken a more extended steam treatment at the higher temperatures tendsmore completely to stabilize the polymer against randomization. Thiswill be more fully indicated in the following specific examples oftypical steam treatment of blocked copolyesters of the fiber and filmforming type in accordance with the invention. In each of these examplesthe blocked copolyester material treated was in finely divided orpowdered form and the polymer was prepared in accordance with the aboveidentified Kibler, Russin and Bell application, Ser. No. 801,705, filedMar. 25, 1959, now US. Patent 3,117,950 entitled Linear AbnormalizedBlock-Type Copolyesters. As previously stated, essentially this processinvolves first preparing a low molecular weight copolyester and heatingthis copolyester at a temperature below its melting point so that aconversion of the random copolyester structure to a blocked copolyesteroccurs. The low molecular weight blocked copolyester is then furtherpolymerized in the solid phase by Well known techniques such as byheating the polymer under vacuum at elevated temperatures until thedesired viscosity is reached. It will of course be apparent that inthese examples we have prepared blocked copolyesters of differentchemical constitution by virtue of the modification of the base polymerpoly(1,4-cyclohexylidenedimethylene terephthalate) with varying amountsof a second dicarboxylic acid and also with ditferent types ofdicarboxylic acids for the second modifying acids.

Example 1.Stabi1ization against randomization of a blocked copolyesterby steam treatment at superatmospheric pressure A 100 gram sample of ablocked copolyester prepared from l,4-cyclohexanedimethanol, 3 molarequivalents of terephthalic acid and 2 molar equivalents of succinicacid in powdered form and having a melting point of 264274 C. and aninherent viscosity of 0.95 was placed in a glass lined one-literautoclave and 10 ml. of water added. After sweeping the autoclavethoroughly with nitrogen, it was sealed and heated to C. The pressurewithin the autoclave was of course the autogenous pressure of watervapor at that temperature. The temperature Was maintained constant at150 C. and the pressure remained constant for a period of one hour. Theautoclave was then vented to atmospheric pressure and cooled. The finalproduct had a melting point of 260265 C. and an inherent viscosity of0.82 (Sample A).

A second sample of blocked copolyester of the same composition wastreated with steam in the above described manner except that theautoclave was held at 150 C. for 0.5 hour before venting. The product inthis case had a melting point of 264267 C. and an inherent viscosity of0.91 (Sample B).

A third sample of the blocked copolyester of the same chemicalcomposition was treated with steam in the same manner as above describedexcept that the autoclave was vented to the atmosphere at approximatelytwo minutes after the temperature of the autoclave reached 150 C. Thefinal product had a melting point of 262266 C. and an inherent viscosityof 0.88 (Sample C).

Precipitation curves were obtained on these three samples A, B and C andon the untreated original blocked copolyester and these four curves werefound to be essentially identical. These three samples and the originaluntreated copolyester are represented in FIGURE by the singleprecipitation Curve F.

The original untreated blocked copolyester and the three steam treatedsamples A, B and C were melt spun into yarn using well known meltspinning techniques. Precipitation curves were obtained on each of thefour yarn samples so produced and these precipitation curves are shownin FIGURE 5. Precipitation Curve I was obtained from the yarn melt spunfrom Sample A which had received one hour of steam treatment at 150 C.Precipitation Curve J was obtained from the yarn melt spun from Sample Bwhich had received 0.5 hour of steam treatment at 150 C. PrecipitationCurve K was obtained on the yarn melt spun from Sample C which hadreceived a very short steam treatment at 150 C. Precipitation Curve Hwas obtained on yarn melt spun from the original unsteamed blockedcoployester.

It can be seen from these precipitation curves that the originalunsteamed copolyester is converted to a completely random copolyester onmelt spinning by comparing Curve H and Curve F of FIGURE 5. It can alsobe seen that the steam treatment described in this example is eifectivein reducing the degree of randomization of the molecular structure bycomparing Curves I, J, and K with Curve H as above described.

It can also be seen that there is a direct relationship between thelength of time which the polymer samples were steamed at 150 C. and theextent to which they randomized on melt spinning. The sample (A) whichreceived the longest time of steaming showed the smallest amount ofrandomizing during the spinning procedure while the sample (C) whichreceived the shortest time of steam treatment showed the greatest degreeof randomization. Under the conditions described in this example a steamtreatment longer than two hours tends to degrade the copolyester used inthis example to an excessive degree.

Attention is now called to Curve L of FIGURE 5 which is termedfour-minute film. This is a precipitation curve obtained, on a filmwhich was pressed from the steam treated Sample A by the followingprocedure. A sample of the material under examination was placed betweentwo polished metal plates. These plates were pressed together with apneumatically operated press, the jaws of which were electrically heatedand the temperature thermostatically controlled. This press served toheat the polymer rapidly to the melting point and simultaneouslycompress it to a film. The film so obtained was held between the platesin a molten state for a period of four minutes at 280 C. The platescontaining the film were then removed from the jaws of the press andquenched in cold water. This film was used to obtain the precipitationCurve L of FIGURE 5.

A comparison of the precipitation Curves L, I, and F of FIGURE 5demonstrates that this four-minute film sample has undergone a slightlygreater degree of randomization than has the yarn sample represented byCurve I. This simple test was adopted as a means of measuring the degreeto which a blocked copolyester had been stabilized by any of theprocedures of the instant invention. It is evident that this four-minutefilm test occasions the use of more severe conditions than areencountered in normal spinning operations. Consequently it is certainthat if a tested polymer shows little or no randomization of its blockedcopolyester structure after being subjected lit to this four-minute filmtest, it may be melt spun under normal melt spinning conditions withlittle or no destruction of the desirable molecularly blocked structure.Subsequent examples will contain frequent references to this four-minutefilm test.

Example 2.A large scale steam stabilization of a blocked copolyester Thepolyester used in this example was prepared fromi,4-cyclohexanedimethanol, 3 molar equivalents of terephthalic acid andone molar equivalent of succinic acid and molecularly blocked by theabove mentioned procedure of Kibler et al. The material had a meltingpoint of 288294 C. and an inherent viscosity of 0.94.

The powdered material was placed in a large vessel equipped with astirrer and steam which had been heated to 125 C. was passed over thepowder While it was stirred to promote contact with the vapor. Thetemperature of the powder was C. during this treatment. A sample of thesteamed polymer was withdrawn after six hours of steam treatment andtested by the above described 4-minute film test. Steaming was thencontinued for a subsequent 9 hours making a total of 15 hours in all andat this time discontinued. The final product was also tested by theabove described 4-minute film test.

Reference is now made to FIGURE 6 where the various precipitation curveswhich were determined on the samples mentioned in this experiment areshown. The precipitation Curve M is the curve obtained from the originaluntreated block copolyester and is identical with that obtained on theblock copolyester after 15 hours of steam treatment. Curve N is theprecipitation curve determined on the film sample pressed in the4-minute film test using a sample of the block copolyester which hadbeen treated for 15 hours with steam. It can be seen that this 15 hoursof steam treatment effectively prevents the rearrangement of themolecular blocks during the 4-minute film test.

Precipitation Curve 0 was determined using the film obtained in the4-minute film test on the polyester sample withdrawn after 6 hours ofsteaming. Precipitation Curve P was obtained on the film pressed in the4-minute film test using the original blocked copolyester. A comparisonof Curves O and P demonstrates that 6 hours of steam treatment wasinsufficient to prevent the rearrangement of the molecularly blockedcopolyester structure and indeed the 6-hour steam treated sample behavedin all respects in a manner very similar to the original blockedcopolyester Which had received no steam treatment.

This experiment demonstrates that the steam treatment of a blockedcopolyester can be highly effective provided it is continued for asutficient length of time.

In actual commercial use, the length of time required to effectstabilization of the molecularly blocked copolyesters by treatment withsteam, can be greatly shortened by the use of superheated steam. Underthese circumstances, the superheated steam is passed through a heatedbed of comminuted blocked copolyester for the required length of timeand the steam penetrates the polymer pellets and inactivates thecatalyst. It is essential in this procedure that a heated bed of polymerbe used, otherwise the steam will condense and the temperature of thepolymer bed will not rise above 100 C. Under these conditions, thepolymer may be treated with steam at atmospheric pressure andtemperatures within the range of 100-200 C. This greatly reduces theduration of steam treatment required to stabilize the molecularlyblocked structure of the copolyesters. The duration of steam treatmentwill vary from one hour to twenty hours depending on the particulartemperature of the polymer bed, a short time being selected for the hightemperature treatment, a long time for the low temperature treatment.

Example 3.Stcam stabilization using superheated steam The polyester usedin this example was prepared from 13 1,4-cyclohexanedimethanol, 3 molarequivalents of succinic acid and molecularly blocked by the abovementioned procedure described in the copending application of Kibler,Russin and Bell, Ser. No. 801,705, filed Mar. 25, 1959. The blockedcopolyester had an inherent viscosity of 0.78.

The powdered blocked copolyester was placed in a layer approximatelythree inches deep on the surface of a porous glass plate. The bed ofpolymer was heated by a furnace to 200 C. and steam superheated by asecond furnace to 200 C. was passed through the bed of polymer for 1.5hours. The final polymer had an inherent It is readily seen that a smallvalue of the precipitation abscissa indicates that the polymer isrelatively insoluble. That is, only a small volume of precipitant isneeded to reduce the percentage transmission of a solution from 100percent to 95 percent. On the other hand a large value of theprecipitation abscissa indicates that the polymer is relatively soluble,that is, a large volume of precipitant is needed to reduce thepercentage transmission from 100 percent to 95 percent. Such a number asthe precipitation abscissa therefore is a convenient means ofcharacterizing the precipitation curves of polyester samples understudy.

PRECIPITATION DATA ON .05% SOLUTIONS IN 60:40 PHENOL-TETRACHLOROETHANEOF MODIFIED LOCKED COPOLYESTERS FROM CIS- AND TRANS- 1,4-CYCLOHEXANE-DIMETHANOL END TEREPHTHALIC ACID Milliliters of Milliliters ofprecipitant 1 precipitant l (methanol) (methanol) Milliliters ofMilliliters of using using precipitant 1 precipitant l copolyester 2copolyester 2 (methanol) (methanol) treated treated Copolyester usingusing with steam with steam composition: original original under undermodifying acid Percent copolyester copolyester 2 pressure pressure inmole percent trans- (not (not at 150 C. at 175 C. of total acids isomersteamed) steamed) for y, hour for hour Example:

4 Glutaric 17% 95 18. 9 22. 9 19. 9 19. 1 5. Sebacic 20% 95 20. 6 26. 331. 3 21. 2 6 95 28.0 35. 4 39. 4 30. 2 7 Isophthalic 78 33. 8 47. 6 39.6 39. 2

1 Required to reduce transmission from 100% to 95% (Figure 2). 2 Fromfilm pressed at 300 C. and held molten for 4 minutes.

viscosity of 0.75 and was found to retain its molecularly blockedstructure on melt spinning.

A similar run was carried out using pellets of blocked copolyester inthe shape of rough cubes inch to a side and the steam treatment wasperformed for six hours at 200 C. The final polymer had an inherentviscosity of 0.70 and was found to retain its molecularly blockedstructure on melt spinning.

The following four examples will serve to illustrate that steamtreatment of blocked copolyesters to prevent randomization of themolecular repeating units is applicable to a wide range of modifiedblocked copolyesters of different compositions. In fact, so far as ourwork indicates, the process is applicable to all copolyesters of thistype. The following tabulation indicates the results obtained when fourdifferent blocked copolyesters having the indicated compositions weretreated with steam in accordance with the invention. Before discussingthis tabulation it will be desirable to refer to the indicated phenomenaby reference to FIGURE 2 of the drawing which is a precipitation curveof a typical fiber-forming copolyester precipitated from 60:40 phenoltetrachloroethane with methanol. Generally speaking, the precipitationcurves obtained on the copolyesters of the subject invention have thesame general configuration. For the purposes of describing theinvention, therefore, it is sufficient to designate by some means thepoint at which the polymer being studied begins to precipitate fromsolution, that is to say, the volume of precipitant necessary toinitiate precipitation of the polyester being studied. In practice it isdifi'icult to define the exact volume of precipitant needed to justexactly initiate the precipitation of the dissolved polymer. It istherefore expedient to select a particular value of the percentage lighttransmission and determine what volume of solvent is necessary toprecipitate sufificient of the dissolved polymer to give this selectedpercentage transmission value. In the following examples this has beendone and the level of 95 percent transmission has been selected.Referring now to FIGURE 2 of the drawing it can be seen that theindicated point X would designate the number of ml. of precipitantrequired to precipitate sufficient of the dissolved polymer to reducethe level of transmission from 100 percent to 95 percent. This value, X,is termed the precipitation abscissa.

It will be noted from the above tabulation that in certain instances thesample of copolyester was in the form of a film which had been pressedat a temperature of 300 C. and held molten for four minutes. The filmform was employed rather than filament form only because it was a moreconvenient method of handling the material and determining the effect onthe temperatures encountered when the material was brought into a moltencondition under temperatures comparable to those employed in thestandard melt spinning and melt extrusion procedures.

A comparison of the figures of column 5 with those of column 4 will showthat in each of the polymers studied a randomization of the originalmolecularly blocked structure has occurred when the polyester sample wasmelted at 300 C. since the solubility, as indicated by the ml. ofprecipitant required to reduce the percentage transmission from 100percent to percent, increases after the untreated polyester is melted.Similarly the figures of column 7 when compared With those of column 4will demonstrate that the steam treatment for /2 hour at 175 C. underpressure serves to essentially completely stabilize the blockedmolecular structure of the copolyester. This is shown by the fact thatafter melting the treated copolyester at 300 C. the volume ofprecipitant needed to reduce the transmission of a solution of thepolymer from percent to 95 percent is approximately the same as that ofthe untreated material. The steam treatment for /2 hour at C. underpressure is seen to be etfective in some cases but not in othersindicating that in some instances this treatment is sufiicient tostabilize the molecularly blocked structure of the polyester but that inmany cases a higher temperature than 150 C. within the range of 100-200C. is needed to effect complete stabilization. It has also been foundthat steam treatment at the higher temperatures of the order of 190 C.and approaching the upper limit of 200 C. for /2 hour tends towardexcessive hydrolytic degradation of the copolyester being treated. Wehave found that the temperature range of to C. is the preferredtemperature range for steam treatment under pressure of the polyestersin accordance with the invention.

As indicated under the general discussion of our invention, preventionof randomization of the molecularly blocked copolyesters can beaccomplished without the use of steam by treating the blockedcopolyester with a small amount of an arsenic compound such as arsenicpentoxide whereby the catalyst present in the copolyester whichcatalyzes randomization is converted to an inactive form which isprobably a molecular complex of titanium and arsenic, the chemicalstructure of which is presently unknown. The examples which followillustrate this general method of neutralizing the catalyst andpreventing the undesired randomization. As will be evident, there areseveral specific methods by which this may be done. In each instance thecopolyester was prepared from l,4-cyclohexanedimethanol, 3 molarequivalents of terephthalic acid and 2 molar equivalents of succinicacid and converted to the molecularly blocked copolyester using one ofthe procedures indicated above and containing as a catalyst titaniumtetraisopropoxide of such a concentration that there is present in thepolymer 150 pars per million of titanium metal.

Example 8.Stabilization against randomization of a blocked copolyesterby arensic compounds The blocked copolyester of the above indicatedchemical composition had an inherent viscosity of 0.76 and aprecipitation abscissa of 41.8. A sample of this blocked copolyester wassubjected to the 4-minute film test and the precipitation abscissa ofthis film was found to be 72, thus indicating extensive randomization ofthe blocked copolyester structure on melting.

Ten grams of this blocked copolyester were dissolved with heating in 125ml. of 'y-butyrolacetone and the hot solution was then poured into 1,000ml. of ethanol to precipitate the polymer. The precipitated polymer wasfiltered off and dried and found to have an inherent viscosity of 0.78.This dried precipitated copolyester was subjected to the 4-minute filmtest and the film was found to have a precipitation abscissa of 68.7.This indicated that the solvent employed, -butyrolactone, had no eitectin stabilizing the molecularly blocked copolyester structure. Anidentical procedure was followed with a second 10 gram sample except 10mg. of arsenic pentoxide was added to the solution. After precipitatingand drying the polymer had an inherent viscosity of 0.85. This materialwas subjected to the 4-minute film test and the film sample was found tohave a precipitation abscissa of 43, which is essentially identical withthat of the original blocked copolyester. This demonstrates that thearsenic pentoxide was effective in deactivating the residual titaniumcatalyst so that the original molecularly blocked copolyester could bemelted and held in a molten condition for at least 4 minutes and stillretain the molecularly blocked structure.

Example 9 The above procedure while demonstrating the effectiveness ofarsenic pentoxide as a means of stabilizing the blocked structure isdifiicnlt to carry out with large samples of polymers. The followingexample describes a procedure whereby large quantities of polymer may betreated with arsenic pentoxide and thereby stabilize the blockedstructure of the polymer.

One thousand grams of blocked copolyester of the same composition asused in Example 8 were slurried with 1,000 ml. of water containing 5grams of arsenic pentovide dissolved in it. After thorough mixing theslurry was evaporated to dryness on a steam bath with occasionalstirring. The final product had an inherent viscosity of 0.80. A sampleof the material was subjected to the 4-minute film test and theprecipitation abscissa of this film was 41.0, a value essentiallyidentical with that of the original untreated blocked copolyester. Thismethod then is as equally e'ltective as that of Example 8 in providing amolecularly blocked copolyester whose molecular structure is stabilizedagainst rearrangement on melting.

Example 10 The following example illustrates another procedure which isconvenient to carrying out on moderately large size samples. It isprincipally dependent upon the use of a carrier or swelling agent topermit the arsenic compound to penetrate the polymer particles andthereby deactivate the catalyst residue.

The carriers which we have found to be especially efiicacious in ourprocess are those selected from the group consisting or butyl benzoate,o-phenylphenol, chlorinated benzenes, dimethyl terephthalate, biphenyland fl-methoxyethyl benzoate.

Ten grams of blocked copolyester of the same composition as that used inExample 8 were slurried in ml. of water containing 0.3 gram of dissolvedarsenic pentoxide and 3 ml. of B-methoxyethyl benzoate as a carrier. Themixture was stirred and heated on a steam bath for 3.5 hours. Theproduct was filtered, dried and found to have an inherent viscosity of0.77. A sample of the final product was subjected to the 4-minute filmtest and the film found to have a precipitation abscissa of 58.4. It canbe seen that while this treatment is not as effective as those ofExamples 8 and 9 in preventing the' rearrangement of molecular blocksduring melting, nevertheless some substantial degree of stabilization ofthe blocked structure is efiected by this treatment. This is shown bythe fact that the precipitation abscissa, after the 4-minute film test,is still considerably less than for the untreated polyester after it hasbeen subjected to the 4-minute film test.

In the examples and the above description and in the claims defining ourinvention we have employed the term stabilization with reference toprevention of the randomization of the molecular blocks of thecopolyester. By this term is to be understood reduction or eliminationof the tendency of the molecular repeat units, which are normallyarranged in discreet clusters or blocks in the polymer to be convertedto a randomly arranged grouping of these units during melting of theblocked copolyester as would be the case in melt spinning of the polymerinto filaments or in melt extrusion into other shaped articles.

It will thus be seen from the above examples and description that ourinvention has solved one of the troublesome problems inherent inemploying blocked copolyesters for the preparation of such products asfibers, filaments, films and other shaped objects, that is keeping thedesirable blocked structure of the copolyester material intact duringthose periods during which the material is subjected to heat in meltingand subsequent extrusion. Expressed in another way, the presentinvention enables one to preserve or stabilize the desirable propertiesof the blocked copolyesters of the type hereinabove specified and tosuch an extent that they may be employed in the production of fibers,filaments, films and other products of improved properties withoutdeterioration of such properties under the conditions normallyencountered in the manufacture of such products.

Although the invention has been described in considerable detail withparticular reference to certain proferred embodiments thereof,variations and modifications can be etfected within the spirit and scopeof the invention as described hereinabove, and as defined in theappended claims.

We claim:

1. The process of stabilizating against rearrangement of the molecularblocks of a high molecular weight, linear blocked copolyester of thefiberand film-forming type derived from the condensation of a member ofthe group consisting of the cisand transisomers of 1,4-cyclohexanedimethanol and at least one dicarboxylic aromatic acidwherein the carboxy radicals are attached to the aromatic nucleus in apara relationship, said copolyester being modified with at least onesaturated aliphatic dicarboxylic acid and having a polymeric molecularstructure in which molecular repeating units (A) and (B), in which Acorresponds to the repeat unit derived from the condensation of1,4-cyclohexanedimethanol with the said aromatic acid and B correspondsto the repeat unit derived from the condensation of1,4-cyclohexanedimethanol with the said modifying dicarboxylic acid, arearranged in clusters or blocks in a regular pattern throughout thepolymer and containing a catalyst which catalyzes randomization of themolecular repeating units at the melting temperature of the copolyester,and which is an oxygenated titanium compound selected from the groupconsisting of the alkoxides of titanium and inorganic complexes derivedtherefrom and present in an amount corresponding to 50500 parts oftitanium metal to a million parts of copolyester., which comprisingtreating the copolyester in comminuted form with rsenic pentoxidewhereby the catalyst is converted into a for min which catalyzation ofthe randomization of the molecular repeating units of the blockedcopolyester is reduced or eliminated.

2. The process of claim 1 in which the dicarboxylic aromatic acid isterephthalic acid.

3. The process of stabilizing against rearrangement of the molecularblocks of a high molecular Weight, linear, blocked copolyester of thefiberand film-forming type derived from the condensation of a member ofthe group consisting of the cisand transisomers of1,4-cyclohexanedimethanol and terephthalic acid, said copolyester beingmodified with at least one saturated aliphatic dicarboxylic acid andhaving a polymeric molecular structure in which molecular repeatingunits (A) and (B) in which A corresponds to the repeat unit derived fromthe condensation of l,4-cyclohexanedimethanol with terephthalic acid andB corresponds to the repeat unit derived from the condensation of1,4-cyclohexanedimethanol with the said modifying dicarboxylic acidarranged in clusters or blocks in a regular pattern throughout thepolymer and containing a catalyst which catalyzes randomization of themolecular repeating units at the melting temperatures of the copolyesterand which is an oxygenated titanium compound selected from the groupconsisting of the alkoxides of titanium and inorganic complexes derivedtherefrom and present in an amount corresponding to 50-500 parts oftitanium metal to a million parts of copolyester, which comprisesdissolving the copolyester in gamma-butyrolactone, adding 0.005-0.5percent by weight of the copolyester of arsenic pentoxide, precipitatingthe copolyester from the solution by adding ethanol, thereto, andfiltering off and drying the precipitated copolyester containing thearsenic compound,

4. The process of stabilizing against rearrangement of the molecularblocks of a high molecular weight, linear, blocked copolyester of thefiberand film-forming type derived from the condensation of a member ofthe group consisting of the cisand transisomers of1,4-cycl0hexanedimethanol and terephthalic acid, said copolyester beingmodified with at least one saturated aliphatic dicarboxylic acid andhaving a polymeric molecular structure in which molecular repeatingunits (A) and (B) in which A corresponds to the repeat unit derived fromthe condensation of 1,4-cyclohexanedimethanol with terephthalic acid andB corresponds to the repeat unit derived from the condensation of1,4-cyclohexanedimethanol with the said modifying dicarboxylic acid arearranged in clusters or blocks in a regular pattern throughout thepolymer and containing a catalyst which catalyzes randomization of themolecular repeating units at the melting temperatures of the copolyesterand which is an oxygenated titanium compound selected from the groupconsisting of the alkoxides of titanium and inorganic complexes derivedtherefrom and present in an amount corresponding to -500 parts oftitanium metal to a million parts of CO- polyester, which comprisesslurrying the copolyester in finely divided form with a 0.15 percentaqueous solution of arsenic pentoxide, and evaporating off the waterfrom the slurry, whereby the treated copolyester contains 0.005-5percent by weight of the arsenic compound.

5. The process of claim 4 in which the slurry contains 1-40 percent,based on the weight of the copolyester, of a carrier selected from thegroup consisting of B-methoxyethyl benzoate, butyl benzoate,o-phenylphenol, chlorinated benzenes, dimethyl terephthalate andbiphenyl.

6. The process of claim 4 in which the slurry contains 1-l0 percent,based on the weight of the copolyester, of e-methoxyethyl benzoate as acarrier.

References Cited UNITED STATES PATENTS 2,437,232 3/1948 Rothrock et a1.3,068,205 12/1962 Smith 260 MORRIS LIEBMAN, Primary Examiner H. H.FLETCHER, Assistant Examiner US. Cl. X.R.

